DESCRIPTION (provided by applicant In the United States, most HIV infections occur in men who have sex with men (MSM). Given the continued high numbers of new HIV diagnoses and differences by race and ethnicity, it is critical to develop a deeper understanding of the context of new infections in order to better target existing resources and to develop new prevention approaches. To examine the roles of place-based and non-individual risk factors systematically, the places where MSM engage in specific behaviors must be systematically defined, and associations between these locations, their characteristics and geographic relationships, and specific HIV-related behaviors must be quantified. By better defining the space in which behaviors occur, place-based studies can also aid in our understanding of structural barriers to early HIV diagnosis and treatment and of structural determinants of risk behaviors. Therefore, an examination of specific locations representing the everyday lives of MSM may be useful in refining the understanding of HIV epidemiology and in targeting HIV prevention and treatment resources. Within this context, this research will address three aims. First, this research will examine the willingness of MSM to specify locations of HIV prevention and risk behaviors using an online map-based tool. Prior studies have validated an online map-based tool for collection of geolocated HIV-care locations among HIV-positive MSM. However, more thoroughly examining places associated with risk and prevention requires a larger sample of MSM, both HIV-negative and HIV-positive, and a willingness of MSM to report information about a broad range of locations. A large sample of MSM will use this online tool to provide various locations associated with HIV risk and prevention. Relationships between a willingness to answer these questions and age, race, and other health and socioeconomic factors will be explored. Second, this research will examine specific locations of risk and prevention behaviors among MSM. Using the concept of activity space, the distance and spatial spread of home and other locations will be quantified, and associations between these geographic distributions and HIV risk and prevention behaviors will be measured. Additionally, these measures may differ by race and level of urbanicity, providing potential information about racial and geographic disparities in HIV Finally, this research will examine migration patterns of MSM. Using data collected from the online survey, life course epidemiologic methods will be used to examine relationships among migration, and HIV risk and prevention behaviors. These methods allow simultaneous exploration of associations between risk and prevention behaviors and both timing and amount of migration. Given our large sample size, potential differences across urbanicity and by race/ethnicity will be observed.